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nuckolls.bob(at)aeroelect
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 Posted: Mon Jan 04, 2021 2:45 pm Post subject: Any ideas where to get electric motor brushes? |
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At 04:11 PM 1/4/2021, you wrote:
| Quote: | --> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com>
Hi Bob It's for a 1941 Monarch EE. It has a 5HP 3 phase AC motor that spins a 4 pole DC generator, the generator is connected to a 2 pole exciter and the DC motor is 4 pole. In 1941 they didn't know how to speed control an AC motor so they did so with a DC motor. I forget exactly the hocus pocus they are doing, it doesn't have a huge tube, but slow speed torque is quite impressive. I need exciter and generator brushes and will probably change the motor brushes as well. All 3 devices have shunt wires. How do I determine what hardness I might want? The exciter brush has 600 on it. The generator brush has 063A on it. I have a call into Monarch, but my generator and exciter may not be stock. Thx. Ron P. |
Hmmm . . . used to teach those systems at Great
Lakes . . . wish I had the books!
Those number may well be brush grades . . . I've
never worked on motors directly but the gurus were
in the next cubicles . . . and I did a lot of test
instrumentation. So my useful info is limited.
If Monarch can't help, a call to one of the brush specialty
houses may yield some up-to-date expertise. Also,
check around for users/parts manuals. I'm seeing
a lot of offers for used/reproduction on Monarch
manuals.
Do look over the McMaster Carr offerings. Also,
this supplier seems likely to have specialty
expertise.
https://www.graphitestore.com/Carbon-Brushes/Brushes
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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rparigoris
Joined: 24 Nov 2009
Posts: 792
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| Posted: Mon Jan 04, 2021 5:42 pm Post subject: Re: Any ideas where to get electric motor brushes? |
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Hi Bob Thx. for info. I actually have an inquiry for quote from McMaster. I printed brush info from graphitestore over the weekend. Minimum of 12 brushes each buy, would require talking to them about hardness and size of pig tail. One size only has a spring over pig tail, but could solder on a terminal. I spoke to a buddy who works for the railroad in the motor rebuilding shop. I'm going to give him a set of old brushes and he will match em up. He said he's pretty good determining the hardness of brushes using his precision calibrated "EyeChrometer". Thx. Ron
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nuckolls.bob(at)aeroelect
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| Posted: Mon Jan 04, 2021 6:06 pm Post subject: Any ideas where to get electric motor brushes? |
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At 07:18 PM 1/4/2021, you wrote:
| Quote: | --> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com>
Hi Charlie
My Monarch EE helped to win WW2. It was owned by the Singer Corporation until the 1970s. Back in the day, 3 phase AC motors couldn't be speed controlled. Thus Monarch has an integral 3 phase AC motor with DC Generator. At the tip of the spinning mass is an Exicter. Some Monarch also used a Magnetron tube. The idea was you could have a variable speed on the fly with good low speed torque. If you just cut voltage on a DC motor you can speed control it but low speed torque suffers. Monarch does some hocus pocus that increases torque at lower speeds compared to just cutting voltage. |
Actually, not all that mysterious. Railroad locomotives
use a similar technology. Generate power with lots of
volts and current that is hooked to the traction motors
full time. Now, just like the regulator in your car
adjusts power output by modulating FIELD current, the
throttle of a locomotive adjusts field current of a small
exciter which in turn drives the field of the traction
generators which in turn powers the traction motors.
The current being handled by the engineer's throttle
is quite small compared to thousands of amps available
to produce motive power.
In the case of locomotives, they're interested in
traction force which is proportional to motor
current. The electronic controls that watch traction
current to achieve conformity with engineer's throttle
commands operate at relatively low power.
In the lathe case, the goal is to achieve constant
speed as opposed to constant torque. Shuffle the
components in the feedback loop a bit and the
'throttle' now produces a command that the electronics
interprets as a 'speed' requirement as opposed to
'torque'.
The electronics work just like the cruise control
on your car. I.e. adjust manifold pressure (motor
current) as required to achieve constant MPH
(spindle RPM). What ever current it takes to do that
is limited only by capabilities of the power
supply WATTS (gas pedal flat on the floor).
The motor controller in the lathe is oblivious
to present voltage/current as long as physical
limits are not exceeded. BTW, if anyone has a
treadmill, the controller for tread speed is
a direct descendant of the system in the Monarch
lathe except that AC/DC conversion is done with
a rectifier instead of a 3-phase motor generator
set.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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nuckolls.bob(at)aeroelect
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| Posted: Mon Jan 04, 2021 6:11 pm Post subject: Any ideas where to get electric motor brushes? |
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| Quote: | | I power my stuff with a 7.5hp rotophase running on 220v single phase including the Monarch. |
Okay, if I interpret your words correctly you
use a single-phase to 3-phase external converter
to power the 3-phase to DC motor-generator in
the lathe which includes a low power exciter (generator)
to manage energy delivered to a work-motor that
powers the head-stock?
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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rparigoris
Joined: 24 Nov 2009
Posts: 792
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| Posted: Mon Jan 04, 2021 6:53 pm Post subject: Re: Any ideas where to get electric motor brushes? |
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Hi Bob
Exactly correct. The work motor is a 4 brush DC motor, probably ~5hp. I had an event about 5 years ago, the timing screws loosened up and the thing slid to full retarded and ripped out a wire. Good thing the wire ripped as running a motor retarded will trash the armature. I timed motor so it was pretty close to neutral, perhaps I gave it 1 degree advanced in forward. Has been running great. To find neutral timing on a motor, you run it forward and reverse and mark where the current draw is identical. I used about 500 rpm. If running forward and reverse neutral is best. For best efficiency if only running forward ~ 5 degrees advanced. Depending on motor, how much heat it can tolerate and how long you plan to run it hard best power is 7.5 to 15 degrees advanced. Many electric motors are 5 degrees advanced, don't run them in reverse unless you neutral time. Ron
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nuckolls.bob(at)aeroelect
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| Posted: Tue Jan 05, 2021 4:00 am Post subject: Any ideas where to get electric motor brushes? |
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At 08:53 PM 1/4/2021, you wrote:
| Quote: | --> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com>
Hi Bob
Exactly correct. The work motor is a 4 brush DC motor, probably ~5hp. I had an event about 5 years ago, the timing screws loosened up and the thing slid to full retarded and ripped out a wire. Good thing the wire ripped as running a motor retarded will trash the armature. I timed motor so it was pretty close to neutral, perhaps I gave it 1 degree advanced in forward. Has been running great. To find neutral timing on a motor, you run it forward and reverse and mark where the current draw is identical. I used about 500 rpm. If running forward and reverse neutral is best. For best efficiency if only running forward ~ 5 degrees advanced. Depending on motor, how much heat it can tolerate and how long you plan to run it hard best power is 7.5 to 15 degrees advanced. Many electric motors are 5 degrees advanced, don't run them in reverse unless you neutral time. Ron |
Yep, that brings back memories. I taught several sections
in ETC School at Great Lakes Naval Training Base for about
6 months . . . loved the job but had to give it up
and come back to Wichita where wages were more commensurate
with cost of living!
Energy conversion in rotating machines was two sections
I taught to Navy recruits. One of my favorite topics
was a thing called the Amplidyne. An electro-mechanical
amplifier widely used on shipboard radar antenna
sweep servos.
https://tinyurl.com/y5ex9ek6
A very interesting critter that took awhile
to wrap your head around!
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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